Prior to the development of the present invention, slackless type drawbar assemblies have been utilized by the railroad industry for several years. Such slackless drawbar assemblies connect the adjacently disposed ends of a pair of railway freight cars together in a substantially semipermanent fashion. As is generally well recognized in the relevant freight car coupling art, these prior art slackless drawbar assemblies have been equipped with a one piece drawbar member as one of the necessary component parts thereof.
In these drawbar assemblies, such drawbar member is rotatably secured at each end thereof into the opening of the center sill portion of each of such pair of freight cars closely adjacent a respective end thereof. This will be the case, even though each of the several different manufacturers and/or suppliers of slackless drawbar assemblies will supply the railroad industry with their own particular design.
It is equally well recognized, in the railroad industry, that at least as many as five such freight cars may be interconnected using these slackless drawbar assemblies. Consequently, assuming for illustration purposes only that there are five such freight cars which have been interconnected in this manner, if only a single end of only a single one of the four such slackless drawbar assemblies required is in need of repair and/or maintenance, then all five of the freight cars must be removed from any revenue generating type service while such repair and/or maintenance is being performed.
Over the past several years, actual experience has rather conclusively demonstrated that these slackless drawbar assemblies will require relatively frequent maintenance. One of the primary reasons why they require a significant amount of costly maintenance is because the design of these prior art type drawbar assemblies inherently requires that a relatively large number of component parts be used.
Additionally, many of these component parts will at least include some surfaces which are frictionally engaged and which, also, must possess the capability of moving with respect to one another during in-track service. These frictionally engaged surfaces will include at least one concave and at least one convex shaped surface as well as a number of flat surfaces.
Furthermore, it is generally well recognized in the art that during service each of these frictionally engaged surfaces will be subjected to rather large forces being exerted on them while, at the same time, some relative movement is occurring between them. In the most extreme circumstances, the forces such frictionally engaged surfaces may be subjected to can be expected to exceed at least about one million pounds.
As would normally be expected, by those persons who are skilled in the mechanical art, the required relative movement between these frictionally engaged surfaces will generate a significant amount of heat energy. This is particularly the case when such frictionally engaged surfaces are being subjected to such extreme loads, which will significantly reduce the useful life span of these components.
Nevertheless, these slackless type drawbar assemblies, which are known to be in use at the present time, have generally provided the railroad industry with a much more modern style freight car coupling arrangement. For example, these slackless drawbar assemblies have substantially eliminated the requirement for a relatively expensive draft gear assembly as well as other freight car coupling components that were normally required before their introduction.
Furthermore, these slackless drawbar assemblies have generally resulted in an overall net decrease in the empty weight of such freight cars. This overall net weight reduction of such freight car is an extremely important factor to be taken into consideration by the user of such railway freight car in view of the ever rising energy cost.
It is believed to be equally well recognized, in the railroad industry, that these slackless drawbar assemblies are primarily installed on selected freight cars which will be utilized in a dedicated service type of application. The reason for this is that most of the freight cars that are utilized in this dedicated type service will not, as a general rule, require that they be uncoupled except for any routine maintenance and/or possible repair being required.
By way of example only, such freight cars which generally are used in such dedicated type service will at least include: coal cars, automobile and light truck transport cars and certain tank cars.
These slackless type drawbar assemblies have, nevertheless, gained a rather widespread acceptance in the railroad industry over the past several years in spite of the number of disadvantages which were discussed in some detail above. This would be expected, however, because there are a number of significant advantages that were gained by such railroad industry, in comparison to the older style standard type coupling arrangements which were and still are being used. Experience has demonstrated that these advantages far outweigh the disadvantages and such slackless drawbar assemblies have proven to the railroad industry over an extended period of time to be quite cost effective,